The field of the invention is that of heaters and the inventions relates more particularly to electrically operated heaters of economical and reliable construction adapted for use as automotive passenger compartment heaters or the like.
Recent trends toward automotive engines operating with greater efficiencies and lower heat rejection rates have progressively reduced the amount of "waste" heat from the vehicle engine which is available for use for heating the passenger compartment. At the same time there is a desire to reduce the compartment heat-up time and to increase passenger compartment temperature. Accordingly, the use of electrical resistance heaters energized from the vehicle power source has been proposed and such electrical resistance heaters using self-regulating heater discs or elements of positive temperature coefficient of resistivity to supplement the conventional hot-water-based heaters have been found to reduce compartment heat-up time and to increase steady state compartment temperature where desired. However, providing such resistance heaters with the reliability and efficiency to operate from the limited available power supply in an automotive vehicle over a long service life subjected to heavy vibrations and wide swings in temperature conditions tends to be expensive. It would be desirable if such a heater made with low cost, high efficiency heat-transfer materials could be provided with a structure which would be economical and convenient to manufacture, assembly and install and which would be efficient and reliable in use. It would also be desirable if such a heater could also be adapted for other fluid heating purposes in automotive applications.